1. Field of the Invention
This invention relates generally to a system for the contained transfer of particulates. The invention relates more specifically to a method and apparatus for transferring hazardous particulates which facilitate the transfer without either exposure of the operating personnel and the environment to the particulate, or outside contamination of the particulate itself.
2. Description of Related Art
In the processing of particulate materials, the particulates must typically be transferred to and from processing equipment, transfer systems, and storage containers. In the pharmaceutical industry, for example, particulates are transferred from a batch processing vessel into multiple transfer containers. Typically, this is accomplished not in an automated fashion but rather through a series of manipulative steps performed by plant operators. A transfer container such as a bag is placed on the discharge port of a piece of equipment, the port is opened to fill the bag, the port is closed, the bag is removed, and the top of the bag is secured.
In the processing and material transfer of hazardous particulates, however, such as highly potent pharmaceuticals, the particulates must be transferred without exposure of the operating personnel to the health hazards associated with the pharmaceuticals. In concentrated form, these pure drugs and/or their intermediates pose a serious health hazard. Exposure to as little as parts per million levels of the drugs can result in chronic health problems and even death. Heretofore, the material transfer was accomplished by personnel wearing personal protective equipment, i.e., full-body protective suits and respirators. Such protective equipment, however, is cumbersome, hot, and uncomfortable to wear; requires operator time to don and doff; and must be washed and incinerated after use.
Additionally, for two reasons, it is desirable that the transfer of such particulate materials be accomplished in a contained manner. First, it is often necessary to protect the particulates themselves from environmental contamination. Second, the particulates being transferred in applications such as the processing of pharmaceuticals are often in a very concentrated state, and the accumulated loss during a series of transfer steps can have a substantial negative impact on the economics of the process.
The means for securing the top of filled transfer containers such as plastic bags has conventionally consisted of twisting the material of the bag lengthwise and tying it off with a wire or plastic closure. While a means for securing the bags by a method such as heat sealing would be more reliable, faster, and convenient, the processing environment has heretofore precluded the use of a conventional heat seal machine. Because of the presence of both flammable gases and combustible dusts resulting from uncontained particulates, the potential for explosion resulting from arcs, sparks, and high temperature exposed surfaces has rendered the use of heat sealing impossible.
In order to provide for the contained transfer of particulates, one conventional process employs a continuous tube of flexible material that is packed onto the discharge port of a vessel. The bottom of the tube is secured by twisting and tying, and the first of a series of bags is filled. The material above the filled bag is then twisted, a lower and an upper tie are applied, and the filled bag is detached by cutting the twisted material between the ties. The material above the upper tie then forms the bottom of the next bag to be filled. While this method provides for some containment of material, a significant potential for exposure arises during the step of cutting the twisted material between the ties. Additionally, an exposure problem arises when the supply of tube is depleted. That is, when it is necessary to remove the top of a tube from the discharge port, the presence of particulate on the tube and the port necessitates that the operators don protective gear. Furthermore, this method fails to address the mechanics of discharging the contents of the filled bag into a vessel in a subsequent processing step.
Furthermore, particulates such as those employed in the pharmaceutical industry are often used in conjunction with solvents and tend to agglomerate within a vessel. In view of the aforementioned value associated with the particulates, however, it is highly desirable to discharge the entire contents of a vessel. Conventionally, if the contents of a vessel were not discharging properly, the vessel would be opened and operators in protective gear would either rod the vessel or enter the vessel to facilitate the discharge. Either method, however, not only interrupts the process but can pose a danger to the safety of the operators and contaminate the product.
Finally, certain conventional technologies employ stainless steel vessels equipped with hermetically sealed ports for the transfer and storage of pharmaceutical products. Such containers, however, along with all of their associated hardware, are expensive to fabricate. Even more importantly, they must be thoroughly cleaned to remove all traces of the particulate prior to reuse in order to avoid quality issues such as cross-contamination. The cleaning and certification program, however, is expensive and not entirely reliable, as it is extremely difficult to remove all traces of particulate from the container.
As an alternative to stainless steel vessels, at least one conventional technology has employed the continuous tube of flexible material described above. While such a transfer container may be disposable, it must also satisfy the rigorous physical requirements imposed by the pharmaceutical industry. That is, the container must possess the required physical characteristics for the particulate transfer service, namely, antistatic properties, flexibility, and high strength. Conventional containers, however, while exhibiting some combination of some of the desired characteristics, have never possessed all of the properties required for use in a system such as that of the present invention.